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Differences in pain perception, health-related quality of life, disability, mood, and sleep between Brazilian and Spanish people with chronic non-specific low back pain Daiana P. Rodrigues-De-Souza1, César Fernández-De-Las-Peñas2,3, Francisco J. Martín-Vallejo4, Juan F. Blanco-Blanco5,6, Lourdes Moro-Gutiérrez7, Francisco Alburquerque-Sendín5,8

ABSTRACT | Background: Cultural and social factors play an important role in the development and persistence of

Low Back Pain (LBP). Nevertheless, there are few studies investigating differences in LBP features between countries. Objective: To determine differences in pain perception between individuals with LBP living in Brazil and Spain. Method: Thirty Spanish individuals and 30 age- and sex-comparable Brazilian individuals with LBP were recruited from the Public Health Services of both countries. The Numerical Pain Rating Scale and the pain rating index (PRI), the number of words chosen (NWC), and the present pain index (PPI) extracted from the McGill Pain Questionnaire were used to assess pain. The Oswestry Disability Index, the Short Form-36, Beck Depression Inventory-II, and Pittsburgh Sleep Quality Index were also applied. Differences between countries and the correlation between demographic and clinical variables in each country were assessed with parametric and the nonparametric tests. Results: A significant Country by Gender interaction was found for the PRI total score (P=0.038), but not for intensity of pain, disability, PPI, or NWC, in which Spanish women exhibited greater pain ratio than Spanish men (P=0.014), and no gender differences were identified in Brazilians. The Spanish group showed a consistent pattern of correlations for clinical data. Within Brazilian patients, fewer correlations were found and all of the coefficients were lower than those in the Spanish group. Conclusion: The pain perception in patients with LBP is different depending on the country. Within Spanish patients, LBP is considered a more global entity affecting multidimensional contexts. Keywords: back pain; cultural characteristics; health evaluation; disabled persons; affect. BULLET POINTS

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Pain perception in chronic LBP could be different depending on the country. Spanish women present greater pain and poorer mental health than Spanish men do. Spanish patients consider that LBP affects multidimensional contexts. The potential relevance of cultural factors in chronic LBP must be determined.

HOW TO CITE THIS ARTICLE

Rodrigues-De-Souza DP, Fernández-De-Las-Peñas C, Martín-Vallejo FJ, Blanco-Blanco JF, Moro-Gutiérrez L, AlburquerqueSendín F. Differences in pain perception, health-related quality of life, disability, mood, and sleep between Brazilian and Spanish people with chronic non-specific low back pain. Braz J Phys Ther.        http://dx.doi.org/10.1590/bjpt-rbf.2014.0175

Introduction Low back pain (LBP) refers to symptoms located under the costal edge and above the folds of the lower gluteus muscles with or without irradiation to the leg1. LBP is classified as chronic when it persists for over 12 weeks2. Non-specific LBP is not attributed to any recognizable pathology (e.g., infection,

tumor, osteoporosis, rheumatoid arthritis, fracture, or inflammation) and it is much more frequent than specific LBP derived from underlying medical conditions2,3. Pain is a complex perceptive disorder associated with social and cultural factors4,5. In fact, recognition of the pain experience is a complex subjective process

Department of Physical Therapy, Universidad Católica de Ávila, Avila, Spain Department of Physical Therapy, Occupational Therapy, Physical Medicine and Rehabilitation, Universidad Rey Juan Carlos, Alcorcón, Spain Cátedra de Investigación y Docencia en Fisioterapia: Terapia Manual y Punción Seca, Universidad Rey Juan Carlos, Alcorcón, Spain 4 Department of Statistics, Universidad de Salamanca, Salamanca, Spain 5 Instituto de Investigación Biomédica de Salamanca (IBSAL), Salamanca, Spain 6 Hospital Universitario de Salamanca Unidad Virgen Vega, Salamanca, Spain 7 Department of Social Psychology and Anthropology, Universidad de Salamanca, Salamanca, Spain 8 Department of Nursing and Physical Therapy, Universidad de Salamanca, Salamanca, Spain Received: May 25, 2015 Revised: Dec. 30, 2015 Accepted: Mar. 03, 2016 1 2 3

http://dx.doi.org/10.1590/bjpt-rbf.2014.0175

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Rodrigues-De-Souza DP, Fernández-De-Las-Peñas C, Martín-Vallejo FJ, Blanco-Blanco JF, Moro-Gutiérrez L, Alburquerque-Sendín F

with important psychosocial and cultural influences. In recent years, researchers have become highly interested in the effects of cultural factors6,7, since these factors have acquired greater importance in chronic pain due to the biopsychosocial model8,9. Although no representative study provides an overall prevalence of LBP in Brazil10, some studies have determined a prevalence of LBP in this country ranging from 4.2%11 to 63%12. As an example, the prevalence of LBP in Pelotas, a medium-sized city of Brazil, has increased from 4.2% to 9.6% within the 2002-2010 period, in part due to an increase in life expectancy in this country13. Being a woman, smoker, and being married13 have been identified as risk factors for LBP, whereas age, body mass index (BMI), exposure to repetitive movements, working in uncomfortable postures13, and having sleep alterations are positively associated with LBP14. In Spain, the prevalence of LBP is around 20% and has remained unvaried in the last five-year period15. As in Brazil, LBP was associated with being a woman, increasing age, low educational level, low earning, and lack of physical activity16. Although it seems that cultural, social, and geographic factors play an important role in the development and persistence of LBP17 and other musculoskeletal complaints18, there are few studies investigating differences in LBP between Europe and South America, probably due to the difficulty in objectively measuring cultural impact in pain19. The research in this area observed medical, physical, and psychosocial differences among patients with LBP20 and other musculoskeletal complaints21-23 in different cultures, societies, and countries. Nevertheless, there is a lack of studies addressing the multi-dimensional features of the LBP presentation in this area24. Therefore, the main objective of the current study was to determine the differences in pain perception between individuals with LBP living in Brazil and Spain. The secondary objective was to determine the differences in health-related quality of life, disability, mood, and sleep quality between both countries and to identify the relations between demographic and clinical data in each country.

Method Participants A cross-sectional design was used in this study. Thirty patients with LBP recruited from the Orthopedic Service at the São Carlos Health Unit (Brazilian Public Health Service) and 30 age- and sex-comparable individuals  2

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with LBP recruited from the Orthopedic Hospital Department at University‑Hospital of Salamanca (Spanish Public Health Service) were included. Participants were recruited through consecutive sampling. To be eligible, they had to suffer from non-specific LBP without referral into the lower extremity for more than 6 months and diagnosed by an orthopedic physician. Exclusion criteria included: 1) age less than 18 years; 2) LBP with a specific underlying medical pathology such as tumor, infection, inflammatory disorders, disc problems, and nerve root compromise; 3) diagnosis of fibromyalgia syndrome; 4) previous lumbar spine surgery; 5) diagnosis of psychiatric illness; 6) presence of other musculoskeletal diagnosis at the time of the study; or 7) refusal to participate in the study. The medical history from each patient was requested from their primary care physician to assess the presence of the exclusion criteria. The same interviewer (DPRS), who was bilingual in Brazilian and Spanish languages and had 6 years of clinical experience, conducted the data collection in both countries. All of the questionnaires were self-administered. All participants read and signed an informed consent form before their inclusion in the study. The current study was conducted following the Declaration of Helsinki and was approved by the Ethics Committee of the University of Salamanca, Salamanca, Spain (code number: 7/2-12). In addition, clinical services of both countries accepted these ethical considerations following an international ethical agreement between both countries. Pain outcomes An 11-point numerical pain rating scale (NPRS, 0: no pain; 10: maximum pain) was used to assess the mean intensity of pain experienced in the last week25. Differences below 1.5 points in the NPRS are not considered clinically relevant26. Patients were also asked about the duration of pain symptoms. The McGill Pain Questionnaire (MPQ) was used to assess pain intensity. Items were joined to achieve three main domains of the questionnaire, i.e., sensory (1-15), affective (16-18), and evaluative (19), as well as the total score or pain rating index (PRI) for each domain. We also considered the number of words chosen by the patient (NWC) and the present pain index (PPI), which describes current pain intensity from 0 (no pain) to 5 (excruciating pain) scales. In the current study, we used the Spanish27 and the Brazilian28 versions of the questionnaire, which have shown good validity. A 30% difference is generally considered clinically meaningful29.

LBP quality of life, disability, mood, sleep

Oswestry Disability Index (ODI)

Sleep quality assessment

The ODI is one of the most frequently used tools for measuring LBP-related disability30,31. The ODI contains 10 questions (rated from 0 to 5 points each) about daily activities, including inventories of pain intensity, personal care, lifting, walking, sitting, standing, sleeping, sexual life, social life, and traveling. The ODI scores range from 0 to 100. Higher scores indicate greater disability. The ODI was validated for LBP and it presents high reliability and consistency (ICC=0.99, α=0.87)32. In the current study, we also used the Brazilian33,34 and Spanish35 adapted versions of this questionnaire. It has been determined that a minimal clinically important difference (MCID) of the ODI is a difference of 10 points and more than 30%29.

The Pittsburgh Sleep Quality Index (PSQI) is the most commonly used tool for a comprehensive assessment of sleep quality46. The PSQI appraises sleep quality over a one-month period through a questionnaire differentiating between good and poor sleepers. It includes 19 self-rated questions and 5 questions answered by bedmates/roommates. The  items use varying response categories that include recording usual bed time, usual wake time, number of actual hours slept, and number of minutes to fall asleep, as well as forced-choice Likert-type responses (0-3). The sum of the scores for the components yields one global score, which ranges from 0 to 21, where higher scores indicate worse sleep quality47. A total score >8.0 indicates poor sleep quality47. Buysse et al.47 reported that the PSQI has good internal consistency (α=0.83) and test-retest reliability (r=0.85). The Brazilian48 and Spanish49 versions were used. No MCID data available for the PSQI.

Health-related quality of life The health-related quality of life was assessed with the Medical Outcomes Study Short Form 36 (SF-36) questionnaire, which assessed eight domains: physical functioning, role physical, bodily pain, general health, vitality, social functioning, role-emotional, and mental health36. After adding the Likert-scaled items, each scale is standardized, so that it ranges from 0 (lowest level of functioning) to 100 (highest level)37. Again, the Spanish38 and Brazilian39 adaptations were used. The SF-36 questionnaire can be also summarized as two health measures: physical component score (PCS) and mental component score (MCS). The PCS is derived from the following domains (physical function, physical role, bodily pain, and general health), whereas the MCS is derived from emotional role, social function, mental health, and vitality domains40. In the current study, we considered physical and mental components of the SF36 questionnaire for the main analysis. As recommended by the IMMPACT group, a 30% change could be used as a barometer of positive clinical difference41. Beck Depression Inventory-II (BDI-II) Participants also completed the Beck Depression Inventory-II (BDI-II), a 21-item self-report questionnaire that assesses affective, cognitive, and somatic symptoms of depression42. The BDI-II showed good internal consistency (α=0.83) and test-retest reliability (0.68‑0.89)42. The Spanish43 and Brazilian44 versions have also shown good internal consistency. The MCID of the BDI-II is 17.5%45.

Sample size calculation The sample size determination was performed using the Spanish software Ene 3.0 (Glaxo Smith Kline, Universidad Autónoma, Barcelona, Spain). The calculations were based on detecting clinical differences of 10 points in the ODI and standard deviation of 13 points29 between groups, with a bilateral significance level of 0.05 and power of 0.80. This generated a sample size of at least 28 patients in each group. Statistical analysis Data were analyzed with the statistical package SPSS version 21.0 (SPSS Inc., Chicago, IL, USA). Descriptive data were collected for all patients. The Kolmogorov-Smirnov test was used to analyze the normal distribution of the variables. Quantitative data without a normal distribution (BDI and MCS) were analyzed with nonparametric tests, and the remaining data with normal distribution were analyzed with parametric tests. Differences in the quantitative variables between countries were assessed with the unpaired Student-t test and the nonparametric Mann-Whitney U-test. The chi-square (χ2) test was used to analyze differences in sex between both groups. A 2-way analysis of variance (ANOVA) test was used to investigate the differences in outcomes with country (Brazil or Spain) and gender (men or women) as the between-subjects factors. The Pearson (r) test and Spearman’s rho (rs) test were used to determine the correlations between Braz J Phys Ther.    

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demographic and clinical variables in each country. The strength of the correlations was classified as weak (r from 0.1 to 0.3), moderate (r from 0.4 to 0.6), or strong (r from 0.7 to 1)50. The statistical analysis was conducted at 95% confidence level.

Results Differences in demographic and clinical data by country and by gender No significant differences between patients of either country were observed for age (P=0.64), gender distribution (P=0.80, weight (P=0.14), height (P=0.06), BMI (P=0.85), years with pain (P=0.74), pain intensity (P=0.24), PPI (P=0.92), PRI total score (P=0.72), or NWC (P=0.11). On the other hand, we found greater disability in Spanish patients than in Brazilian people (mean difference MD, 95%CI: 9.87, 18.06-1.68), P=0.02). Table 1 summarizes demographic and clinical data of Spanish and Brazilian patients with LBP. The ANOVA revealed a significant Country * Gender interaction for PRI total score (P=0.04), but not for intensity of pain (P=0.88), disability (P=0.35), PPI (P=0.75), or NWC (P=0.06). Spanish women with LBP exhibited greater pain ratio than Spanish men (MD, 95%CI: 18.06, 3.84-32.28, P=0.01), whereas no gender differences were found in Brazilians. Table 2 shows demographic and clinical data of Spanish and Brazilian patients with LBP by gender.

Quality of life Significant differences between countries were observed for physical (MD, 95%CI: 17.06, 5.98-28.15, P